By using a computer as a slide projector, a number of special effects are employed in multimedia presentations. The special effects are produced by what is known as multimedia files in which are stored sound effects, video, animation, and the like. Typically, a multimedia presentation comprises a sequence of computer screens organized in slide format. Each slide has on it what are termed objects. Anything may be an object. The objects are linked to multimedia files that contain audio or visual information. Typically, the multimedia files are stored in digital form, although they may be stored in analog form if the appropriate interface equipment and drivers are provided. Typically, the presentation includes only a reference to a segment of any media source or file. These are called clips. Only the reference may be stored in the presentation file. The multimedia files are usually vendor-supplied and are accessed by way of a Media Manager. Clips are start and end position references to a multimedia file. Defining a clip determines the starting and ending points in a multimedia file or device. The term "linking" is analogous to message sending. An object is said to be "linked" to another object when it sends a message to it. An example of linking could be, "When Button 1 Mousedown, Play Animation of Circle 1." Button 1 is linked to Circle 2.
Occasionally, when a presentation is taken to the field, the presenter will discover during the presentation that a particular link can not be found. For example, when a button is clicked on a certain slide, music is supposed to be played from a particular MIDI (Musical Instrument Digital Interface) file. The presenter clicks the button, and the presenter is embarrassed to find that no music plays. Either the MIDI file has been lost, the multimedia link has been broken, or the file is hidden in a directory not currently being searched by the Media Manager when it goes through the directories in the drive path.